The present invention has particular utility in connection with the prevention of shock waves in sheet materials as well as in preventing sheet material backup as the material is advanced out of a processing apparatus, and is described herein as applied to such use.
Material processing apparatus such as, drum plotters typically operate by performing work operations on elongated sheets of material fed from a roll. In known plotters, a tool carrying tool head is mounted on an elongated support located above and extending across the elongated sheet of material. The tool head moves in one (y) coordinate direction back and forth across the support's length as the sheet of material itself is advanced by the plotter in another (x) coordinate direction perpendicular to the first coordinate direction and longitudinal of itself so that the entire surface of the work material can be reached by the tool head with the tool moving along straight or curved lines relative to the sheet of material.
Subsequent to the performance of the work operation the elongated sheet of material is typically advanced out of the plotter in a vertically downward direction towards the floor or other horizontal surface such as, for example, a table top. Often, the sheet materials being processed are somewhat stiff and therefore do not immediately collapse when the leading edge of the sheet material contacts an obstruction. Therefore, a problem sometimes occurs when the edge of the sheet material, as it is being fed out of the plotter, contacts a floor or other horizontal surface. When this happens, the sheet material, rather than simply collecting on the floor, tends to kink and may back up or send a shock wave through the sheet material to the particular area upon which the tool head is performing the work operation. This can detrimentally affect the operation of the tool head and thereby damage the item being made.
In addition to the foregoing, the speed at which the sheet material is fed out of the plotter is directly proportional to the magnitude of the shock wave that will be generated when the leading edge of the sheet material impacts the floor. Therefore, there is a current need for a means by which the plotting speed can be maximized, and the impact speed of the sheet material minimized.
Accordingly, it is the general object of the present invention to provide an apparatus which prevents kinking, or the generation of shock waves in a sheet material as it is being processed.
A more specific object of the present invention is to provide a device which decreases the speed at which the sheet material contacts a horizontal surface as it is advanced out of the plotter while maximizing the speed at which the sheet material is plotted.